The lateral line system of fishes and amphibians provides a particularly favorable system in which to elucidate the mechanisms underlying neural evolution. The phylogenetic distribution of lateral line receptors indicates that one or more lines of neuromasts and, frequently, all electroreceptors have been lost independently in several radiations and that electroreceptors have, more rarely, re- evolved. Because phylogeny is the result of changes in the ontogenies of an ancestral population and its descendants, one must understand the development of lateral line receptors in order to understand the mechanisms underlying their evolution. A lateral line placode is the primary Ontogenetic unit that generates neuromasts and electroreceptors in salamanders and those bony fishes that have retained primitive electroreceptors, but comparable information does not exist for teleost electroreceptors that have re-evolved. Therefore, a detailed description of lateral line receptor development in the electroreceptive channel catfish will be undertaken using scanning electron microscopic, histological and immunohistochemical techniques (aim 1). Comparing the ontogenetic sequences for primitive and re- evolved receptors can establish where changes have occurred but can not establish the mechanisms underlying these changes. To determine these mechanisms, a logical first step is a better-understanding of the possible role of cephalic neural crest in the induction of lateral line placodes. This will be examined by cell lineage studies involving immunohistochemistry and embryonic transplantations in salamanders (aim 2). Finally, Hox genes, a newly discovered network of transcription factors are believed to play a major role in the patterning of neuroectodermal tissues and may also be involved in the individual specification of lateral line placodes. To test this hypothesis axolotl embryos (late gastrula or neurula stages) will be exposed to retinoic acid, which is known to produce transformations in the expression of Hox genes, and the distribution and innervation of lateral line receptors will subsequently be examined for resulting homeotic transformations (aim 3). Together, these studies will provide critical insights regarding the development of teleost electroreceptors, the mechanisms of their development, and the role of Hox genes in patterning head organization.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS024669-12
Application #
2883635
Study Section
Hearing Research Study Section (HAR)
Program Officer
Finkelstein, Robert
Project Start
1987-04-01
Project End
2001-02-28
Budget Start
1999-03-01
Budget End
2001-02-28
Support Year
12
Fiscal Year
1999
Total Cost
Indirect Cost
Name
University of California San Diego
Department
Neurosciences
Type
Schools of Medicine
DUNS #
077758407
City
La Jolla
State
CA
Country
United States
Zip Code
92093
Gibbs, Melissa A; Northcutt, R Glenn (2004) Development of the lateral line system in the shovelnose sturgeon. Brain Behav Evol 64:70-84
Schlosser, G; Northcutt, R G (2001) Lateral line placodes are induced during neurulation in the axolotl. Dev Biol 234:55-71
Schlosser, G; Northcutt, R G (2000) Development of neurogenic placodes in Xenopus laevis. J Comp Neurol 418:121-46
Northcutt, R G; Holmes, P H; Albert, J S (2000) Distribution and innervation of lateral line organs in the channel catfish. J Comp Neurol 421:570-92
Schlosser, G; Kintner, C; Northcutt, R G (1999) Loss of ectodermal competence for lateral line placode formation in the direct developing frog Eleutherodactylus coqui. Dev Biol 213:354-69
Cruce, W L; Stuesse, S L; Northcutt, R G (1999) Brainstem neurons with descending projections to the spinal cord of two elasmobranch fishes: thornback guitarfish, Platyrhinoidis triseriata, and horn shark, Heterodontus francisci. J Comp Neurol 403:534-60
Rupp, B; Northcutt, R G (1998) The diencephalon and pretectum of the white sturgeon (Acipenser transmontanus): a cytoarchitectonic study. Brain Behav Evol 51:239-62
Wright, L S; Kornguth, S E; Oberley, T D et al. (1998) Effects of lead on glutathione S-transferase expression in rat kidney: a dose-response study. Toxicol Sci 46:254-9
Daggett, D A; Oberley, T D; Nelson, S A et al. (1998) Effects of lead on rat kidney and liver: GST expression and oxidative stress. Toxicology 128:191-206
Northcutt, R G (1997) Evolution of gnathostome lateral line ontogenies. Brain Behav Evol 50:25-37

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